<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<div>
    <input type="text" id="n1">
    <input type="text" id="n2">
    <input type="button" value="加" @click="f(1)">
    <input type="button" value="减" @click="f(2)">
    <input type="button" value="乘" @click="f(3)">
    <input type="button" value="除" @click="f(4)">
</div>

<p></p>
<script src="https://cdn.staticfile.org/vue/2.2.2/vue.min.js"></script>
<script>
    let v = new Vue({
        el:"body>div",
        data:{},
        methods:{
            f(x){
                let i = document.querySelector("#n1");
                let j = document.querySelector("#n2");
                let d = document.querySelector("p");
                if (isNaN(i.value)){
                    d.innerText="输入错误"
                    return;
                }
                switch (x) {
                    case 1:
                        d.innerText=i.value*1+j.value*1;
                        break;
                    case 2:
                        d.innerText=i.value-j.value;
                        break
                    case 3:
                        d.innerText=i.value*j.value;
                        break;
                    case 4:
                        d.innerText=i.value/j.value;
                        break;
                }
            }
        }
    })
</script>

</body>
</html>